The typical Leighton tube consists of a glass tube to be used in conjunction with a flat thin glass cover slip. Tissue cultures are grown in such a Leighton tube by placing appropriate media in the tube along with the cells to be cultured. The use of such tubes, with their concomitant cover slip, allows the user to stain cultures. Such staining capability is valuable in a variety of experimental tests situations. Further because of the flat shape of the cover slip and its small size, it can be attached to and preserved along with reports associated with such tests or experiments.
Despite the usefulness of the Leighton tubes heretofore used they have certain drawbacks. First, they are difficult and expensive to manufacture. Second, because the cover slips of the prior are made of glass and therefore are flat in shape, they are difficult to handle and retrieve from the inside of the tube. Furthermore, being made of glass, they are prone to breakage. It is among the purposes of the present invention to eliminate some of the disadvantages associated with glass Leighton tubes.
One object of the present invention is to provide a Leighton tube assembly which can be manufactured easily and cheaply from injection moldable plastics.
Another object of the present invention is to provide a Leighton tube with a dam or baffling means to prevent the flow of liquid media out of the tube.
A further object of the present invention is to provide a Leighton tube assembly having a cover slip with a handle so that manipulation of the cover slip (as with tweezers) is facilitated.
Another object of this invention is to provide a cover slip in which the handle is so arranged that the aforementioned dam does not interfere with the proper positioning of the cover slip in the tube.
Still a further object of the present invention is to provide a Leighton tube assembly have a cover slip with a handle which is displaced from the plane of the culture segment thereof so that the latter may lie upon the wall of the tube while the former clears the dam located in the neck of the tube.
Another object of the present invention is to provide means to prevent the light weight cover slip from floating in liquid media placed within the Leighton tube.
Yet another object of the invention is to provide a Leighton tube having a dam and cover slip so constructed that the liquid media placed within the tube chamber does not escape by capillary action.
A further object of the present invention is to provide a Leighton tube assembly with a cover slip the culture segments of which can be cut by a scissors or a knife so that a plurality or portions thereof, with adhering culture, can be attached to more than one report for preservation therewith.
A further object of the present invention is to provide a Leighton tube assembly with a cover slip made of a transparent material which is inert to most chemical solvents so that said cover slip may be used in connection with most experimental and staining treatments which a user may wish to apply. The transparency facilitates accurate observation of cultures grown on the slip.
Another object of the present invention is to provide a Leighton tube in which the cover slip is treated to be wettable so that cells grown within the tube will adhere to the cover slip, which then makes it possible for a user to stain and otherwise test growths on the cover slip.
Still a further object of the present invention is to provide a Leighton tube in which the culture segment is automatically properly positioned in the tube chamber upon insertion of the cover slip.
The Leighton tube of the present invention comprises a tube and a cover slip. The tube has a neck and a chamber, the chamber being toward the closed end of the tube. The neck has a dam formed in it, which is in a blocking position with respect to a flat portion extending longitudinally from the closed end of the chamber. Being of a complicated shape, this tube cannon be made in one piece by an injection molding process because the molds could not be removed from the chamber region after formation. This problem is overcome by making the tube in two pieces. The neck piece, in which the dam is located, can be formed by injection molding material such as polystyrene around two interior molds that can be extracted from either end of the neck piece after formation. The chamber piece only requires but one internal mold and is molded out of the same polystyrene material. After the two pieces are molded, they are welded together to form the complete tube.
Also molded into the closed end of the tube is a guide rib which is located centrally in the upper portion of the closed end and is adapted to guide the cover slip into proper position as it is inserted and to hold the cover slip in place and to prevent it from floating when liquid media is in the tube. The relative ease with which the parts of the tube may be injection molded, with the dam and the ribs located therein, is indicative of the possible savings associated with the cost of manufacture of these tubes as compared with that of conventional glass Leighton tubes.
The cover slip is also molded from a plastic material. It is desirable that the material out of which this cover slip is made be both transparent and unaffected by most chemical solvents. The requirement of transparency arises out of the need for detailed inspection of the cultures grown on the cover slip. The desirability of the relative chemical inertness is a consequence of the needs of users who wish to do experiments and tests on the material on the cover slip. Because the tests and experiments often involve the use of organic solvents which can eat away many plastic materials, the material should be chemically inert. A material having both the desired qualities and which can be used in the molding of the cover slip is called TPX.
The cover slip though formed in one piece has three distinct parts. The culture segment which is flat, a handle and a connecting segment which joins the culture segement and the handle. The culture segment has dimensions such that it may lie flat upon the flat portion of the wall of the chamber with its distal end located underneath the guide rib formed in the closed end of the tube. The connecting segment rises from the culture segment and connects to the handle which lies substantially in a plane parallel to that in which the culture segment lies and is of a height above the culture segment such that when the cover slip is located in its growth position within the tube, the handle clears the dam located in the neck of the tube. The connecting segment rises at an angle that is steeper than the angle the dam makes with the flat portion of the tube, so that when the cover slip is in position the connecting segment and the dam have a wedged shaped gap between them. This gap prevents the liquid from rising in the space between the connecting segment and the dam by capillary action.
The handle is of length such that it does not protrude from the open end of the tube when the cover slip is in its growth position and therefore it does not prevent the cap from being screwed onto the tube. The handle is serrated and further because the handle is not in contact with the walls of the tube when the slip is in place, the handle may be grasped easily and securely, by tweezers, for easy manipulation. To strengthen the handle, ribs are formed along its sides.
Also molded into the neck of the tube is a spacer rib which is located centrally on the chamber side of the dam. This spacer rib maintains a separation between the dam and the cover slip connecting segment, which prevents the undersirable capillary action. The spacer rib also is angled and located so that it acts cooperatively with the guide rib to guide the cover slip into position and hold it in place.